Lubricating grease composition



Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE GREASE COMPOSITIONlfaul fi s nith, J13, Westfield, and Arnold J. Morway, I iahway, N, 1.,assignors to Standard Oil Development oe oean a corporation of DelawareNdDrawing. Application November 1, 1949, SerialNo. 124,942

eon a (01. 252-41) invention pertains to lubricatinggrease,

compositions oi-iinproved structural'stabilityicontaining hydrbxfy'etheracidsoapsl' It rela es else.

nc ed;c ei j vd methera pha c en f his. en ral th ns-lee BirtB'tBttl Q Oand 1 B (4, B iEF QQQE where R1 and R2 are aliphatic hydrocarbon groupsof 3, to, 12 carbon atoms each, preferably, but not necessarilysaturated, R3. is an aliphatic, hydrocarbon group, of 2 to 6. carbonatoms, and m, is an integer of at least 1, preferably 1 to. 2. 0]: l to.3. Preferably, R1 and R2 arev 6 to 10 carbon atoms h nd the o a q i iscar on at R3, contains preferably 2 to 3 carbon atoms. I he a ig t us.nta ns. refer b o 16 to 24 ca fbon'atoms, about, being specificallypreferred. twill be not d that he (De-Rs. rad calin, th s hain mail be re te 2 to 3 imes. Q e e imqre lneaxti u a an ac d o i rmu s Wa lace H?FQE H. A Q 3 i. e, the ether oi 12 hydroxy stearic acid, is found to hean especially suitable material for forming the soap, but th entir claof om lo us sawrated acids, within the limits of chain length mentionedabove. ma be em l e D ti of; certain unsaturated acids, such asricinoleic,

may lso. be. used. emcneth sp c fic, compound which may be employedare.8-(I -hYG fQXY-E Vh: oxy) -stearic acid, 12-(fit-hydroxy-ethoxy),-stear ic. acid, 12 (e hydroxy-ai-propoxy)ricinoleic.

acid, 10-(B-hydroxy-isobutoxy) -pa1mitic acid, mixed hydroxy-alkyletherv derivatives, of hydroxy acids prepared by chlorinatin fatty.acids and hydrolyzing the'chloroacids, etc.

In order to produce .the branched chain hydroxy ether. acids mentionedabove, the, following metm 0d may be pursued. Hydroxy. acids, forexample those. of natural occurrence, such as ricinoleic (hydroxy.stearic). acid, may. be, reacted with an olefin oxide such as. ethylene,oxide or, propylene oxide. The reaction maybe, carriedout. without acatalyst, but it is, preferable to use a Eliiedel Crafts. catalyst suchasBFs, SnCh, or thelike,

For. example, 0.1 mol (3. gof; hydroxy, stearic. acid was. dissolved intoluene, containing 0.5 1nl.- of SnClr. The. mixture was stirred rapidlyin a B-necked flask while 20 g. (0.45 mol) of ethylene oxide was bubbledThe reaction temperati 1re was kept between, 5,01. and 609-. ,C. Thesolyent. was removed by. keeping. the flask ina steambath for severalhours. The remaining. product, which solidified on cooling, was analyzedfor acid and found to have an acid. value, of 0.21 1 centi-equiva lents.per gram, corresponding. to better than a purity of acid. The smallnon-acidic resi: dueprobably was toluene. With longer treatment on thesteam bath, the acid may be made practi cally pure.

Other. hydroxy acids, both aliphatic and aromatic, appear to, reactsimilarly. The production of the hydroxy ether, acids per se forms nopart of the present invention but it may be noted that the. process justdescribed appears to be applicable" to various hydroxy. fatty acids andto aromatic acids such as, salicylic acid, and th like. The former maybe said to have the general formula mentioned abQYe. The branched chainaliphatic acids of fairly. high. molecular, weight are the ones ofinterest in gre se m nufactur It is particularly to be noted that thealkylene oxide radical may. occur. only once. or. it may, be repeatedtwice or more. In general, the acids actually produced in practiceare amixture of branchdchain compounds having, respectively, one'alkylene'e'ther and avatar even more alkylne ether groups. Acids withmore than two "such groupsm senesapp ar "tobeprese'nt in very qea'1"'s,'if at all, under the reaction conditions (1 tribesabjove,butiifiderother condition they may appear 'insub ta tia'lprostrtions.

e er i 9 r ases FO l i P P e aps of these various products areundoubtedly affected by the number of alkylene oxide radicals in series.The invention includes the various reaction products just mentioned and,in particular, greases containing soaps of acids at least with 1 to 2and in some cases, more alkylene oxide groups.

The specific formulas of the reaction products of olefin oxides andhydroxy acids may be written in several ways, including those givenabove. The products may take the formula where R1 and R2 have the samemeaning as above and where R3, R4, R and R6, or any of them, may beeither hydrogen or a methyl group. This alkylene-oxide group 'may occuronly once or more than once, e. g., twice or more. Hence, m is aninteger whose value may be 1, 2, 3, or even more, but usually 1 or atmost 2.

The branched chain hydroxy ether acids just described may be convertedto soaps by using the appropriate metal oxide, hydroxide, or carbonate,as will be obvious to those skilled in the art. 7

The alkali metal soaps, especially the lithium soaps. of such acids, areparticularly meritorious, but the calcium, barium and aluminum soapsalso may be used, and indeed the metals in general. These" soaps may bemixed with each other and/or may be used in admixture with conventionalsoaps, e. g., the alkali or alkaline earth metal, or aluminum soaps ofstraight chain fatty acids. In addition, conventional salts and/or soapsof low molecular weight, such as alkali or alkaline earth metalacetates, acrylates, propionates, furoates, and the like, may also beincluded in the ingredients. The combination of low molecular weightsalts with soaps of higher molecular weight is often advantageous, as isnow well-known in the art.

Soaps of the type characterizing the present invention may be used(alone or in combination with other andconventional thickeners, asmentioned above) to prepare greases of mineral lubricating oils,synthetic oils, or mixtures thereof. The following detailed examplesshow lithium and calcium soaps used in various oils and combinations ofoils, but the invention clearly is not limited to the lithium and/ orcalcium base greases or to the specific lubricants claimed. Theim'provement in stability and other characteristics of lithium soapgreases is noteworthy, and this is a preferred product.

The proportions of ingredients used may be varied within usual limits,although it should be noted-that somewhat smaller quantities of thebranched chain hydroxy ether acid soaps of this invention may berequired in some case to thicken .a grease to a givenconsistencythan isrequired of conventional soaps. As little as about 3% of the new typesoaps, or as much as 35% to 40%, based on the weight of the totalcomposition, may be used. According to the present invention, thenewsoaps may be used alone or they may be combined with conventionalsoaps. In the latter case, the hydroxy ether acid soap preferably shouldcomprise at least one-third of the total soap. Hence, a greasecomposition of the present invention will comprise at least 1%, up to amaximum of about 40% by weight, of hydroxy ether acid soap, with a totalsoap content of 3 to Preferred ranges are 6 to 20% total soap, whichpreferably includes not less than 2% of the hydroxy ether acid soap andat least 4% of additional thickener, the latter being either the same orsome conventional soap.

In the specific case of lithium soap greases, the use of about 8 to 12%total soap is particularly preferred, at least one-third of which soapis of hydroxy ether acid. Where firm consistency is desired with minimumsoap consumption (the lithium soaps being relatively expensive) acombination of about equal parts of conventional lithium soap (e. g.,lithium stearate) and the hydroxy ether acid soap is particularlydesirable. In the case of calcium greases, somewhat higher quantities,e. g., 20% or more of soap, appear to be preferable.

As suggested above, the present invention includes notonly a newcomposition but an improved process of preparing a composition havingexcellent properties of stability resistance to moisture, and the like.A grease is prepared, preferably by adding 1 to 40 parts by weight ofthe branched chain hydroxy ether acid (containing one or more alkyleneoxide groups) to 10 to 96 parts by weight of mineral base lubricatingoil. The mixture of oil and acid is next heated moderately with stirringto a temperature between 100 and 200 F., for example F. At this point,an aqueous solution of a saponifying agent, such as lithium hydroxide,sodium hydroxide, calcium hydroxide, or the like, is added in suitablequantity to neutralize the acid. An aqueous solution of lithium orcalcium hydroxide, for example, is added at the temperature of about 150F.

The mixture is next heated to a temperature of at least 212 F., andpreferably a little higher, to dehydrate the grease andthereafter thetemperature is further raised to cook the grease and form a greasestructure. The cooking temperature is between 300 and-500 F., about 400F. being preferred. During the various steps just described, the productis continuously stirred, preferably with a mechanical stirrer.

After cooking, the grease is cooled in thin layers, either in a close.clearance mechanical cooler or by pouring into thin layers in coolingpans or drum chilling. Thereafter, the product is homogenized andpackaged.

Where it is desired to prepare a grease having extremely goodtemperature characteristics, for example, a grease to be used both atvery low and very high temperatures as in the lubrication of airplaneinstruments, it may be preferable to use a substantial quantity of asynthetic oil, such as di-2eethylhexyl sebacate or the tri-ethyleneglycol ester of 2-ethylhexanoic acid, or other related branched chainesters having outstanding temperature viscosity characteristics. Wheresuch lubricants are to be used, it is preferred to prepare the soap inmineral oil, as described above, adding the synthetic oils after cookingto avoid hydrolysis of the esters. The proportions of mineral oilandester oil may be varied, but preferably at least 10% of thecomposition should be of mineral base oil. Aside from requirements forhigh and low temperature operation, the

mineral base greases are quite satisfactory in themselves.

If it is desired to prepare a lubricant which contains no mineral baseoil, a preformed soap.v

should be used and dispersed thoroughly into the synthetic. oil; so.asto. obtain. a; good; grease structure. This may be done-.by-methodswells in. the; art. Conventional. greases. prepared;v eithen by forming:the. soaps.- of; straight chain. fatty acids. in situ or prepared. from;me.- formed soaps; are commonly deficient in: strut?-- tural stabilityespecially when subj ected: to. heavy mechanical working. Greasesprepared accord?! ing to: the method described above. are; superior: inthis respect.

Thus, conventional lithium. base: greases. pre pared by forming: thelithium. soap. of stearic acid, hydrogenated fishoil acids, and the.like; in lubricating oil are structurally unstable. to l'ong'andseveremechanical working. Thisinstae bility is readilyshown by workingthe.-grease. inthe standard ASTM? grease worker for about. 1000 strokes. Theconventional lithium soap. greases break down into a semi-fluid productunder this treatment.

On the other hand, greases prepared from the lithium soaps of hydroxyfatty acids, such as hydroxy stearic acidwherein the hydroxy group isattached: directlytothe main and. only hydrocarbon. chaizr. have goodstructural, stabilitybut they tend to. harden, under, high shearing;stresses. They also; possess comparatively. poor water resistingcharacteristics.

Accordin o. the present. invention,. gre ses prepared from: hydroxyether acids. or. the. t p

described. above. have both good. structural. stability to mechanicalworking and a. good resistance: to. water; They. do not-harden under.-high shearing? stresses;

As another feature of the present invention, it: is: found that. thecombination ofv the soaps oi: hydroxy'" other: acidswith. conventionalsoa s. y elds: a; crease: of. firmer consistenc for; a given quantityof. soap: than the conventional prod- Where: mixed; soaps; are so u ed.as; previously mentioned; the; hydr xy etheracid sea-P should; compriseat, least about one-third of; thetotalisoap; employed. Bet-terresultsare obtained if approximatel equal quantities of conventional. orstraight chain soap such as lithium stearate and the soap of the presentinvention are combined.

The invention will. be more fully understood by reference. to thefollowing examples:

Example I 10.00% hydroxy' ether acid of; invention. of molecular weight.about; 363 (derived from. ethyl-- one oxide, treatment of- IZ-hydroxystearic 1.23%. ItiOH-HiO 68.77% di-z -ethylhexyl. sebaoate 20.00%-reflned coastal type. mineral oil, of: 37

S. U. s. viscosity at: 2.10? F.

The hydroxy ether acid. evidently was. a mi ture of products containinga single ethylene oxide radical and two, or possibly more, ethyleneoxide radicals in series. It was added to the cold mineral oil:andcharged to a fire heated grease kettle. The mixture was next warmedto 150 F. while agitating. Th lithium hydroxide, dissolved in boilingwater, was next added to neutralize the acid and form the soap inmineral oil. After the mass was dehydrated (225 F.), the esterconstituent. was added and the grease further heated to 400 F. The hotmolten grease was then poured onto a drum chiller for quick cooling; Themolten grease oncooling' was collected by scraping from thecreasekettle. on passing: through. a. Qorncll; homogenizer The; product- Qt:stable struts ture and had a texture.

Properties:

Free alkalinity (as LiQH).% 0.1.0.. ASTM worked penetration 77-Penetrationaiter work g. 1.. ..0.00.st.1:Qke

ASTM' worker employing fine hole worker plate mm../ 10 2,97

Dropping: point: u'- 351$ Appearance. tExcellent, smooth, buttery-Prepared in similar manneras shown in Example I; The grease was of a:softconsistency having a worked penetration at 350 mm./10 and a droppingpoint. of 326 F.

Example: 1 1' Equal. portions; f the. two. gr ases. p pared, above. weremixed. and; heated to. 4500* E: The; hotmolten grease at 400- F.,, wapoured; into pans in shallow layers and cooled". Aftercool:- ing, thegrease was of excellent, smooth struc-- ture.

Worked penetration. at, 77 pm-[101... 3,10 Dropping point F. 3,44Example. L1!

5.00% lithium stearate 5.00% lithium; soap.- of; acid. f iny riti0. .1.as. in;

, Example 90 .00% mineral. oil. in. Example The combined? soaps werevdispersed in. the mineral oil: at 4.20 E: and; c oled. By either rapid;cooling" h nla ers n cooling-- pans) or slow cooling, anexeellent smoothgrease was obtained.

Worked; penetration, 60. strokes 77f Ea.

a Penetration. after 1.40.000 strokes worker- A few experiments. havebeen run also to determine the efiectiveness or the. calcium soaps asthiokeners for mineral oil: and estersp boiling water for 3 ,hours.

Klan acid, derived by treating l z-hydroxy stear-ic acid with ethyleneoxide andhaving a molecular Weight of 363was employed. The followinggreases were prepared.

Example VI 20.00% hydroxy-ether acid 2.30% hydrated lime 77.30%naphthenic-type oil of about 100 S. U. S. viscosity at 100 F., and 40 S.U. S. at 210 F.

Example VII 20.00% hydrofol acids 54 (hydrogenated fish oil acids)Stearic acid could be used instead.

3.00% hydrated lime 77.00% mineral oil as in Example VI Prepared similarto above Example VI.

' EzrampZe VII I.

The two greases of Examples VI and VII were mixed together in equalproportions and heated to 250260 F. (Grease fluidized at 275. F.) Oncooling, an excellent smooth greaseofexceHent structure stabilitywasformed. Ioi about 220 mm./10 penetration. 4

Dropping point, 288 F. Boiling water test-10 grams of grease placed inNo disintegration .or separation of the grease. No cloudiness in Inpreparing greases according to this invention;.-the:. particular metaloxide or hydroxide used for-saponification should be selected that-ismost suitable for the intended purpose. The lithium and'calcium basegreases have good water resistance. Lithium greases show. superiorstability but of course the calcium greases are less expensive. Sodabase greases may readily be prepared in the same manner butthey'are-"less water resistant. Mixed base greases of these and othermetals also may be prepared.

While the foregoing examples all relate 'to'" the lithium and thecalcium soaps, some of which are commonly more'difiicult to prepare thanthe more conventional metal base products, it will be understood thatvarious other metal bases will be used with equal-facility and withcomparable beneficial results. It will also be understood thatconventional additives maybe included in the! grease compositionswithout altering theimbasic properties; Thus, the usual apti-oxidants,corr s oain b eek n aasem ext p e liegsejcbp ij wherein R1 and R2areialkyligroupslof .3 to -12 2-to 6 carbon atoms;v

2. A'lubri'cating grease composition consisting" essentially of alubricating oil thickened to a grease consistency with 3 to 40% of soapof allphatic carboxylic acid, at least one-third of said soap being 'ametal soap of branched chain hydroxy aliphatic acid of 18 to 23' carbonatoms, the hydroxy group being on a side chain and the acid radicalcontaining at least one C2. to C3 alkylene ether group in a side chain.

3. A lubricating grease composition consisting essentially of alubricating oil thickened; to agrease consistency with a metal soap ofaliphatic carboxylic acid, said thickener comprising at least one-thirdpart by weight of a metal soap of a hydroxy ether acid having thegeneral formula Rs I'M e -0E (I: R5 in a1- HRz'oooH wherein R3, R4, R5,and Re are each selected from the class consisting of methyl groups andhydrogen and wherein R1 and R2 are each alkyl groups of 3 to 12 carbonatoms, totaling 14 to 18 carbon atoms. v

4. Composition according to claim 3, wherein said oil comprises asynthetic ester oil; I

5.-Composition according to claim 3, wherein said oil is mineral oil.

6. Composition according to claim 3, wherein said soap of hydroxy etheracid is an alkali metal soap Y 7. Composition according to claim3,'wherein said soap of hydroxy ether acid islithium-soap.

8. A lubricating grease composition consistin essentially of alubricating oil thickened to a grease consistency with about 8 to'12 byweight, based on'the total composition, of soap" of :aliphaticcarboxylic acid which includes at'least' one-third part of lithium soapof an acidhaving the general formula u I 5-3 m-bn-RJ-do. onwherein R1and R2 are alkyl groups of 6 to 10 carbon atoms each, totaling 14 to 18carbon atoms, n is 2, and m is an integer of 1 to 3.

9. Composition according to claimiZ-wherei'n the metal of the soap is analkali metal.

10. Composition according to claim 2 wherein the metal of the soap is analkaline earth metal.

11. Composition according to 'claini'i2 wherein the metal of the soapcomprises lithium: 12'. Composition according?to-iclainrrztwhereiir themetal of the soap comprises calcium,-'

13. Composition according toclaim 3, wherein thehydroxy ether acid hasthe formula c lmcmon F 0 cngcnmtnqcnm ooon" 15. The process of preparinga stable metal base grease which comprises-adding; toflO parts by weightof a branched chain hydroxy ether carbon atoms each and R; is an alkylgroup of saturated aliphatic acid of 17 to 23 carbon atoms and havingthe hydroxy group on a side chain, to 10 to 96 parts of mineral baselubricating oil, heating to a temperature of 100 to 200 F., adding anaqueous solution of a metal base to saponify said acid in situ in saidoil, heating to a temperature of at least 212 F. to dehydrate, adding asynthetic ester oil, further cooking to a temperature of 300 to 500 F.to form a grease structure, and cooling in thin layers.

16. Process according to claim 15, wherein the metal base is lithiumhydroxide.

1'7. Process according to claim 15, wherein the metal base is calciumhydroxide.

18. Composition as in claim 8, wherein the lubricating oil comprises asubstantial proportion of di-2 ethylhexyl sebacate.

19. Composition as in claim 8, wherein the lubricating oil comprises asubstantial proportion of tri-ethylene glycol ester of 2-ethylhexanoicacid.

PAUL V. SMITH, JR. ARNOLD J. MORWAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,435,328 Guest Feb. 10, 19482,435,829 Guest Feb. 10, 1948 2,436,347 Zimmer et a1 Feb. 17, 19482,450,221 Ashburn et a1 Sept. 28, 1948 2,457,640 Bruson et a1 Dec. 28,1948 2,475,589 Bondi July 12, 1949 FOREIGN PATENTS Number Country Date615,188 Great Britain "Jan. 3, 1949

1. A LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OF LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH 3 TO 40% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF METAL SOAP OF ALIPHATIC CARBOXYLIC ACID, SAID METAL SOAP COMPRISING AT LEAST ONE-THIRD PART OF A SOAP OF AN ACID HAVING THE GENERAL FORMULA 